There are two kinds of Heinlein fans. Many meet in the middle in loving works such as The Moon is a Harsh Mistress, but the divide comes between those who love his earlier books, his juveniles, the more straight-line traditional adventures, and books such as Stranger in a Strange Land and Time Enough for Love. Well, I'm the kind that's not a fan of this book. In fact, I after this book I gave up on reading the books Heinlein wrote later--so I've read all the novels published before this one, but none of the later ones such as Friday, Job, The Cat Who Walks Through Walls.
I'm just no fan of polyamory, particularly as Heinlein presents it, with this idea that monogamy is unnatural (as is the incest taboo, and oh, clothing). Well, it may be true the typical man doesn't want exclusivity--but the typical woman doesn't like to share and be shared either--I think if polyamory were natural, we'd see it pretty often whatever a society's mores--just as homosexuality has been widespread even when a cultural taboo. And for all the seemingly "liberated" sex in this, I don't find Heinlein's female characters believable as human beings. Somehow this bothers me more in the post-Strangers in a Strange Land books than it does in his space operas written in the fifties--maybe because there it's more forgivable he's a product of his times.
That said, this still gets three stars because there's still always things in Heinlein's books to love--even in the ones I like the least. In Stranger in a Strange Land I loved his spoof of astrology and his fish out of water hero trying to "grok" human beings. With Lazarus Long, born in 1912 and now the oldest human living, there is wisdom to be had, loads of quotable lines and quite the ride here. It's been several years since I've read this and yet I still remember parts vividly (although not necessarily the good parts. Why, oh why did Heinlein think Lazarus lusting for--and having sex with--his mother was a good idea?). Mind you, as I said there are two kinds of Heinlein fans. I may not be the right kind to love this book--but there are those who think this is the best book he ever wrote. So at least try it for yourself.